Comparing Two Arrays in JavaScript

Comparing two arrays in JavaScript looks easy, but it is not as easy as you think. It becomes difficult due to the JavaScript nature of handling objects and references. Besides the primitive data types (like numbers or strings), arrays are the reference data types in JavaScript, which means that if two arrays have the same elements but have different references or memory locations, they are not considered to be equal. There are multiple techniques available for JavaScript array comparison depending on the structure and order of the arrays involved.

In this blog, you will explore different methods to compare the arrays in JavaScript, their advantages, and best practices to know the best way to compare two arrays in JavaScript.

Table of Contents:

• Method to Compare Two Arrays in JavaScript
  • Method 1: Use JSON.stringify() for Quick Array Comparison
  • Method 2: Compare Arrays Using a for Loop
  • Method 3: Convert and Compare Arrays Using join()
  • Method 4: Use every() to Check Element-wise Equality
  • Method 5: Deep Compare Arrays using Lodash isEqual()
  • Method 6: Compare Arrays Without Order Using Set
  • Method 7: Sort and Compare Arrays (Unordered Check)
• Performance & Use Case Comparison of Each Method
• Practical Use Cases of Array Comparison in JavaScript
• Conclusion

Method to Compare Two Arrays in JavaScript

JavaScript provides various methods to compare two arrays. In this section, we will show you how to check if arrays are equal in JavaScript using different built-in and library-based approaches.

Method 1: Use JSON.stringify() for Quick Array Comparison

It is one of the simplest ways to compare arrays in JavaScript. You can first convert them into JSON strings and check whether the resulting strings are equal or not. It returns an answer in the form of true or false.

Example:

Output:

Explanation: In this example, you are using JSON.stringify() for comparing arrays. It has a simple and more readable syntax.

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Method 2: Compare Arrays Using a for Loop

The for loop is a more traditional method for comparing two arrays. It involves checking each element one by one from both arrays.

Example:

Output:

Explanation: In this example, a traditional for loop is used to compare the two arrays. First, it checks for the length of both arrays; if they are not equal, then it returns “Not Equal”. But if they are equal, then the for loop iterates over each element of the array and compares every element.

Method 3: Convert and Compare Arrays Using join()

The join() method converts an array to a string, and after doing this conversion, we can do a simple comparison between the two strings.

Example:

Output:

Explanation: The join() method also converts an array into a string and then checks for the equality of both strings. If it is found equal, then return true. Otherwise, return false.

Method 4: Use every() to Check Element-wise Equality

This method checks that every element of one array matches the corresponding elements of the second array.

Example:

Output:

Explanation: In this example, the Array.prototype.every() method checks each element in the array using its index (idx) and prints the output in the form of true or false.

Method 5: Deep Compare Arrays using Lodash isEqual()

You can compare arrays using lodash isEqual. For comparing nested arrays (deep comparison), the .isEqual() method from the Lodash library is used.

Example:

Output:

Explanation: An External library like Lodash, which is used for comparing arrays in JavaScript. If arrays contain nested arrays, then using the .isEqual() method of the Lodash library is the best choice. For scenarios involving nested arrays in JavaScript, comparing arrays with nested values can be effectively handled using Lodash’s deep comparison utility.

Method 6: Compare Arrays Without Order Using Set

If the order of elements doesn’t matter, you can compare unordered arrays in JavaScript using sets or sorting techniques. An unordered comparison means comparing the elements without thinking about the order in which the elements are compared, and a Set allows you to compare arrays without considering element order.

Example:

Output:

Explanation: In this example, the Set method is used to convert an array into a set, then, after converting it into a set, JavaScript performs the comparison.

Method 7: Sort and Compare Arrays (Unordered Check)

To check if two arrays are the same without order, you can use a Set-based comparison or sort both arrays before comparing them. Sorting both arrays before comparing them is another method for comparing arrays in JavaScript, but this is difficult and least recommended because you need to write extra code for sorting the arrays.

Example:

Output:

Explanation: In this example, the arr.slice().sort() is used for sorting the array, then .join() method is used for converting it into a string and performing comparison.

Performance & Use Case Comparison of Each Method

Here is the performance comparison between all the methods used for comparing two objects in JavaScript:

Practical Use Cases of Array Comparison in JavaScript

• Validating User Input: Comparing two arrays in JavaScript is helpful in comparing user-selected options with stored choices.
• API Response Comparison: Checking the output responses of the APIs helps in making the comparison.
• Shopping Cart Updates: Used for detecting changes in cart items.

Conclusion

To compare two arrays for equality in JavaScript, you can choose from several methods based on your use case. For simple or shallow checks, use JSON.stringify() or join(). For deep comparison, especially when arrays contain nested values, use Lodash’s isEqual(). If you need to compare arrays without considering order, sorting, or Set-based techniques are effective. These JavaScript array comparison methods help ensure accurate and efficient results.

Comparing Two Arrays in JavaScript – FAQs